Five warning signs showed up on the dashboard and multi-information display. The fan for the hybrid battery pack started running all the time. A trip to the dealer determined that cell #5 in the battery pack was weak.

Fortunately it was under warranty. Otherwise the service guy thought it would take $3,300 to replace it. He said it's the first time he's had to replace one of those cells.

Mileage dropped by about 3 mpg recently. I'm blaming that on the bad cell.

Thanks for posting that...it may be the first case reported of an individual cell replacement. It's just a recent change in their service procedures to do that and they have to try to closely match age and mileage of the replacement cell to that of your car...they aren't just supposed to pop in a brand new one.

Five warning signs showed up on the dashboard and multi-information display. The fan for the hybrid battery pack started running all the time. A trip to the dealer determined that cell #5 in the battery pack was weak.

Fortunately it was under warranty. Otherwise the service guy thought it would take $3,300 to replace it. He said it's the first time he's had to replace one of those cells.

Mileage dropped by about 3 mpg recently. I'm blaming that on the bad cell.

Warnings: /!\ + (!) + VSC + Check Engine + red car with "!"

The dealer replaced it free within 24 hours and the car is running fine again.

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Roughly how many miles was on your Prius when this happened and what year is the car?

I'm curious because 2 years ago when I had my Honda Insight I replaced the batteries. They were warranted for 80,000 miles and they went out at 96,000. Total battery cost was $7000 and $1000 for labor. Fortunately Honda covered it as if it was still in warranty. When I bought my Prius, I was under the impression from some research I have done, that the cells last much longer than they used to. Thanks.

Are you sure they just replaced the sub-pack? $3300 is close to what it costs to have the whole battery replaced.

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Within 24 hours of getting my car back from the shop, someone backed into it while it was parked on the street. Now I have to get the front bumper replaced. Bummer.

So while I was at the dealer this morning I asked specifically whether they replaced just the bad cell or the whole battery pack. They said they replaced the whole hybrid battery pack.

I'd call that good news since now I don't have to worry about a mismatched cell.

Sorry if that first post was misworded, I wasn't really aware of the issue of replacing just the cell vs the whole pack.

The car is a 2006 Prius with 18,000 miles on it. Pretty new. I've heard that electronic-type components tend to either break early in their life or last a really long time. I'm guessing this is one of those early breakdowns.

It's safer and less stressful on battery management if you replace the whole battery. Though you -can- replace one cell, you will get less-than-optimal performance depending on management. That's how I understand it.

Realize I am the kind of dork who enjoys engineering better batteries for cordless telephones and other such nonsense. I have learned that swapping out one of three cells for a higher-capacity (more milli-amp hours) cell makes the battery seem to perform worse. Probably because the battery management systems charge it until only the one cell will take a charge, but that cell always runs short.

1) There are no procedures written up to do this by Toyota (I've looked). 2) They do not have the individual cells in their standard inventory, even though there is a part number. 3) It truly is a rare event, so little money would be saved by Toyota....but some $$$ would be lost in repair pack sales. 4) They would not get back the whole battery pack to find out if just the cell went bad or if there was an external event (e.g manufacturing damage of failed cell and adjacent cells).

Whole battery replacement looks to be the better option for warranty repairs but other views are valid.

Long before the first Prius left the showroom more than a decade ago, Toyota developed a detailed procedure for recycling hybrid vehicles' nickel-metal hydride (Ni-MH) batteries. In the years since, Toyota also has developed a way to postpone recycling by keeping hybrid batteries in service longer.
To the consumer, recycling the battery from a Toyota hybrid is totally invisible: Owners don't have to take any action or pay anything. For hybrids that wind up in a scrap yard, there's a toll-free number on the battery pack: Callers learn they'll get a $150 reward for bringing the unit to a Toyota or Lexus dealer. Toyota then ships the battery pack to a single recycling center. Every component-from plastic to precious metal-is recyclable. With nickel prices near all-time highs, it's likely a large portion of recycled batteries will quickly become part of other products.
Toyota batteries are designed to last a long time. It appears this goal is being achieved: www.hybridexperience.ca reports that two '01 Prius taxis Human each accumulated more than 200,000 miles. That's more than double the warranty, which is eight years or 100,000 miles (or 10 years or 150,000 miles for states that follow California regulations).
When the rare issue occurs, packs that are still under warranty are replaced with all-new units. According to Jim Gatzke of Toyota's National Alternative Fuel Vehicle Service and Support group, the problem is usually with only one of the 28 modules that comprise the battery pack. For vehicles no longer under warranty, Gatzke's team has developed a process to recondition battery packs for maximum life.
â€œThe module must be replaced with one that matches the chemistry of the other 27 modules,â€ says Gatzke. To match the chemistry of the battery pack being reconditioned, the replacement module must be harvested from a battery pack out of a vehicle of about the same age and mileage. With the module replaced, the battery pack should last another half-dozen or more years, Gatzke says.
While Toyota Hybrid batteries are expected to last the entire life of a vehicle, a reconditioned pack costs about a fourth as much as an all-new unit, which should make Toyota hybrids attractive to used-car buyers, according to Gatzke.

Bummer, I thought there was a ray of hope that Toyota techs were
becoming competent/confident about jumping inside the packs.
Looks like Toyota is still having them treat the whole thing
as a hazardous black box.
.
WRT the "battery reconditioning" stuff, well, that's lovely, but
how do you get hold of this group that's supposedly researching
it and actually obtain their finely crafted work if and when you
need it? Without a phone number where you can hear "we'll fix
ya right up", it sounds like marketing spin.
.
_H*

secondly, past warranty where the owner is covering the problem out of pocket, you run the risk of other cells going bad later, through circumstances that are likely not related to anything the tech did. then you have the owner returning, screaming about how they just paid $x to replace cells and why is it bad again, this is on the dealer's head to fix.

in some cases it may be true, but i can't tell you how many coincidences happen that the dealer did not cause but they cover anyway. expensive coincidences (ie hybrid batteries) are very strongly avoided.